(1) Field of the Invention
This invention relates to an automatic vibration molding machine for green sand molding for casting.
(2) Prior Art
Conventionally, adopted types of green sand molding machines are roughly divided into three, i.e., a jolt type, a squeeze type and a blow type.
A jolt type green sand molding machine comprises a flask placed on a table of a molding machine in which sand is filled, an air cylinder installed under the table to which compressed air is blown, and a piston combined with the table. The piston is blown up together with the table by the compressed air, and the table falls free by exhausting air at a certain level of height. Then, the table and the cylinder collide with each other and the sand in the flask is squeezed down toward the pattern underneath by innertial force of the sand itself. Thus, the jolt type is provided with a basic mechanism of a conventional green sand molding machine.
The squeeze type green sand molding machine comprises a mechanin which the green sand in a flask is pressed downward into the flask by a pnewmatics by an air cylinder or oil hyraulics (instead of these means there are means using a diaphragm). Both driving types, in anyway, use a pressure plate whose size is a little smaller than the inner size of the flask (The cylinder and the pressure plate can be plural).
Otherwise, the squeeze type green sand molding machine is provided with a squeeze mechanism in which a flask filled with green sand on the pattern is raised by compressed air or oil hyraulics of a squeeze cylinder together with the table of the upper part of a cylinder toward the pressure plate which is fixed above the flask.
The blow type is a method of filling green sand in a space between the pattern of the flask and the pressure plate by utilizing an air flow. It is known that there are a blow-in and pressure type and a decompression and vaccum type.
The above-mentioned conventional green sand molding machine is a combination of a main mechanism for clamping a flask and a drafting mechanism for separating the clamped flask and the pattern (a stripper type in which a flask is drafted upward from the fixed pattern and a pattern-draw type in which the pattern is drafted downward from the fixed flask), and various types of molding mechines such as a flask type, and a snap flask type in which the flask is installed in the molding machine.
In the molding machine simply having functions of a jolt type and a squeeze type, a match plate of upper and undersurface type as a pattern is used and a tapered snap flask is also used, and it is carried out that first of all, a drag is formed and reversed and its cope is formed, and their draft is also carried out manually. In this manual work, it is advantageous that skillful arrangement is made according to the experience of an operator, so as to accommodate complex molds. However, there are such disadvantages that in molding the manual operation needs a great effort for reversing both of the cope and the drag simultenously, drafting and also for lifting the flask and the pattern by hands. As a result, such skillful operators, who may use this type of molding machine, have become reduced year by year.
Further, the flask is limitted to such a flask of small type which may be delt with hands, and the actions of jolt type generates metallic sounds and vibrations due to fall and strike of a table to cause sometimes break of the table, and also there may be raised a problem of working environment due to propagation of vibrations from the molding machine to the operator via the floor.
Where such a molding machine having functions of jolt type and squeeze type provides a draft function of stripper (or pattern-draw), the flask may be adapted for a mold of middle size since it is not necessary to hand the flask, and it is seldom to use a snap flask. Therefore, such a molding machine is normally operated in semi-automatic operation and therefore it is advantageous that it may be used for various purposes with respect to any type of pattern.
However, where the molding machine becomes bigger, the jolt sounds and vibrations become greater, and further since its squeeze pressure becomes several tens of tons, it may increase danger of break of parts of the machine. Further, since it is necessary two patterns for the top flask and the bottom flask, it has to use two molding machines, or it needs a changing mechanism for changing the pattern for the cope and the drag alternately. This causes a disadvantage of cost-up for installation.
Contrary to this, the blow squeeze type, which provides a blow mechanism for filling green sand in the place of a flask while transferring the green sand with an air flow, is normally suitable for a small size mold of mass production that is speedy in molding and a number of molding machines are in a type of snap flask. Further, such a molding machine is worked almost automatically except core setting operations and sometimes the molding machine provides an automatic core setting device.
This type of the molding machine has an advantage of rapidly forming a mold, but it provides direction for filling the green sand with an air flow, and as a result, it raises a problem that it may form a shadow according to the shape of a pattern but cannot give a correction to the portion where filling of the green sand is insufficient.
Further, the pattern wears rapidly with sand blast and as a result, the pattern is frequently made of metalic material and its cost becomes high. Furthermore, it increases consumption of parts for blow operation, so that its maintenance cost also goes up, and the price of such a molding machine becomes high inevitably since an oil pressure device is frequently used for its squeeze operation.
In anyone of the jold type or the squeeze type or its improved type, the processes of filling, pressing and forming of the green sand are carried out at the same place and with a series of flow, and therefore there is no way, but a process for a new flask must be started after completion of molding of a flask. This raises a problem that molding productivity does not go up.
In view of the above-mentioned problems of the prior art, this invention has an object to provide an automatic vibration molding machine which has a high productivity to present a green sand mold of sufficient compression without using an oil pressure device of high cost as pressure means, and to prevent propagation of vibrations to a floor.
To achieve the above object, an automatic vibration molding machine for green sand mold according to the present invention comprises a plurality of vibration proof springs 5 fixed onto a base 4 which is fixed to a floor, a lower frame 3 set and fixed on the vibration proof springs 5, ascent and descent cylinder means 25 with a lock mechanism fixed to the lower frame 3, an ascent and descent table 23 setting thereon a flaskb filled with green sand therein and constructed to go up and down between an upward pressing and forming position and a downward predetermined position, an upper frame 1 disposed via an intermediate frame 2 positioned standingly on the lower frame 3, a vibration head 11 having at least one vibration motor 10 for vibrating a pressure plate 13 via pressure air spring means 12 expansible and contractible in up and down directions, said vibration head being suspended from the upper frame 1 via a head-ascent and descent frame 17, and ascent and descent means 14 for ascending and descending the vibration head 11 to ascend and descend the pressure plate 13 between an upmost position for separating the pressure plate 13 from the flaskb by contracting the pressure air spring means 12 and a descent position for expanding the pressure air spring means 12 to press the green sand, whereby the green sand of the flaskb may be compressed and formed by the pressure force of expansion of the pressure air spring means 12 and the vibration force of the vibration motor 10 mounted on the vibration head 11, as well as the vibration which is propagated to a pattern c from the upper frame 1 via the lower frame 3, the ascent and descent cylinder 25, and the ascent and descent table 23.
In the present invention, it is preferable that the automatic vibration molding machine further comprises a frame stabilizing device 6 for changably shifting the lower frame 3 between an ascent position for rigidly supporting the lower frame 3 by expanding the vibration proof air springs 5 upwardly and a descent position for descending the lower frame 3 at the time of molding so as to flexibly support the lower frame 3 by means of the vibration proof air springs 5, when the flask b is taken in and taken out of the molding machine, wherein said frame stabilizing device 6 comprises a plurality of cam followers 9 for supporting the lower frame 3 from the beneath thereof, a frame stabilizing cylinder 7 operatively connected to the cam followers 9 to rotate the cam followers 9, and said cam followers 9 are arranged along the sides of the lower frame 3 which are opposite to each other, so as to rotate in opposite directions each other.
Further, it is preferable that the ascent and descent cylinder means 25 with a lock mechanism ascends with oil by means of an air-oil converter 27 and is locked by means of a ball valve 28 as the valve is closed.
Furthermore, it is preferable that a rotary fork 33 for setting the flask b at both end portions thereof to ratate laterally about a vertical axis, said rotary fork 33 being arranged on the base 4, and a green sand supplying station A A and a molding station B, arranged respectively at positions leaving 180 degrees therebetween.
As will be seen from FIG. 6, showing vibration molding, the green sand filled in the flask b increases its fluidity and smoothly goes into shadow portions of the pattern so as to be pressed minutely and to obtain a constant hardness of the mold in a short time by receiving three kinds of force and a vibration which is propagated to the pattern c from the vibration motor via the upper frame 1, the intermediate frame 2, the lower frame 3, the ascent and descent cylinder means 25 and the ascent and descent table 23. Namely, the three kinds of force are pressure forces derived from a dead load of each of the vibration head 11 and the pressure plate 13 in a free state (free fall condition), a pressure force caused by expanding the pressure air spring means 12, and a vibration force caused by the vibration motor 10.
In addition to this, by providing the vibration proof air springs 5, the vibration of the vibration head 11 may prevent a bad influence that the vibration is propagated to the floor and the operator or other implements of the molding machine. Further, since the flask b is positioned and fixed stably in a molding position (ascent) by means of the ascent and descent cylinder means 25 with a lock mechanism, the flask may receive the vibration of the vibration head 11 and the pressure of the pressure air spring means 12, so as to surely carry out minute filling of the green sand.
For reference, the dead load of each of the vibration head 11 and the pressure plate 13 and the pressure caused by expanding the pressure air spring means 12 and the pressure force derived from the vibration force of the vibration motor 10, generate a value of face pressure less than about 2 kgf/cm2(That is about one fifth in comparison with the oil (air) system of the prior art.). However, the present invention obtains a hardness of mold around 90 points. For example, in the oil pressure system of the prior art, it neccessitates a power of generating 10 kgf/cmxc2x15 kgf/cm2, in order to obtain the said hardness of mold.
In the present invention, at the time of taking the flask b in and out from the molding machine, where the frame stabilizing device 6 is provided for changably shifting the lower frame 3 between an ascent position for rigidly supporting the lower frame 3 by expanding the vibration proof air springs 5 upwardly and a descent position for descending the lower frame 3 at the time of molding so as to flexibly support the lower frame 3 by means of the vibration proof air springs 5, when the flask b is taken in and taken out of the molding machine, wherein said frame stabilizing device 6 comprises a plurality of cam followers 9 for supporting the lower frame 3 from the beneath thereof, a frame stabilizing cylinder 7 operatively connected to the cam followers 9 to rotate the cam followers 9, and said cam followers 9 are arranged along the sides of the lower frame 3 which are opposite to each other, so as to rotate in opposite directions each other, the following functions will be expected.
Namely, as seen from FIG. 5 of descriptive view, the frame stabilizing device 6 becomes possible to change easily and very rapidly the take-in process and the take-out process of the flask other than such a manner of supplying air under pressure to and exhausting air from the vibration proof air springs 5.
Further, instead of descending the lower frame 3 by exhausting air from the vibration proof air springs 5 or contacting the lower frame 3 with the base 4 to place the lower frame 3 to fix its position, fix of its position of the lower frame 3 by ascending the lower frame 3 with cam function, so that it becomes possible not only to change its position rapidly but also smoothly fix its position without shock at the time of its position fixing.
Furthermore, by rotating the cam followers 9 in opposite directions with each other, it is not afraid that the cam followers 9 are rotated reversely and downwardly due to any vibration or load from the upward, since the cam followers 9 are fixed after they passed each of the dead points in different directions. Therefore, the lower frame 3 may be supported in a state that they are mechanically stable.
Further, where the ascent and descent cylinder means 25 with a lock mechanism ascends with oil by means of an air-oil converter 27 and is locked by means of a ball valve 28 as the valve is closed, the ascent and descent cylinder may be locked rigidly by a lock of the oil pressure circuit while using air as a power source of its operation, and as a result, the locking operation may be surely carried out while saving its manufacturing cost.
In addition to this, where a rotary fork 33 is provided for setting the flask b at both end portions thereof to rotate laterally about a vertical axis, said rotary fork 33 being arranged on the base 4, and a green sand supplying station A and a molding station B, arranged respectively at positions leaving 180 degrees therebetween, it becomes possible to progress a sand filling process and a molding process simultaneously, so that its productivity may be increased.
Thus, the present invention has obtained the following advantages.
Namely, with the pressures caused by a dead load of the pressure plate and by expanding the air spring means as well as the vibration force of the vibration motor which are propagated to the green sand in the flask or with the complex forces of the vibration which are propagated to the pattern via the upper frame, the intermediate frame and the lower frame, it becomes possible to make a green sand mold of sufficient hardness in a short time notwithstanding it generates a small surface pressure, and further it may obtain an advantage economically that manufacturing costs of the molding machine can be lowered since the machine does not necessitate accurate and big oil cylinders (or air cylinders).
Furtheremore, in spite of compression molding of green sand utilizing mainly vibration, it becomes possible to intercept propagation of the vibration to a floor, and so it is advantageous that a bad influence of vibration to an operator and other implements may be prevented.
Other advantages in detail of this invention are as described hereinbefore.